Radiation patterning tools are utilized during semiconductor processing to pattern radiation (such as, for example, ultraviolet light). The patterned radiation is projected against a radiation-imageable material (such as, for example, photoresist) and utilized to create a pattern in the radiation-imageable material. The utilization of patterned radiation for forming a desired pattern in a radiation-imageable material is typically referred to as photolithography. The radiation-patterning tools can be referred to as photomasks or reticles. The term “photomask” is traditionally understood to refer to masks which define a pattern for an entirety of a wafer, and the term “reticle” is traditionally understood to refer to a patterning tool which defines a pattern for only a portion of a wafer. However, the terms “photomask” (or more generally “mask”) and “reticle” are frequently used interchangeably in modern parlance, so that either term can refer to a radiation-patterning tool that encompasses either a portion or an entirety of a wafer. For purposes of interpreting this disclosure and the claims that follow, the term “reticle” is utilized to generally refer to any radiation-patterning tool, regardless of whether the tool is utilized to pattern an entirety of a substrate or only a portion of the substrate.
An exemplary method of utilizing a reticle to pattern radiation is described with reference to FIG. 1. A reticle construction 10 is shown provided above a semiconductor substrate 12. The substrate 12 has a radiation-imageable material 14 thereover. Radiation 16 is passed through reticle construction 10. The radiation is patterned by construction 10 to form a desired radiation pattern which is directed toward radiation-imageable material 14 and ultimately is utilized to form a desired image within the radiation-imageable material. The desired image can include a pattern for forming semiconductor circuit elements, such as, for example, a pattern which can be transferred to one or more materials underlying the radiation-imageable material 14 to form patterned electrically conductive circuit elements (for instance, source/drain regions, wordlines, bitlines, capacitor electrodes, etc.) and/or patterned electrically insulative circuit elements (for instance, gate dielectric, capacitor dielectric, etc.).
The reticle construction 10 comprises a base 18, projecting features 20, and windows 22 between the projecting features. The projecting features can comprise phase-shifting material (such as, for example, silicon nitride, silicon oxynitride, molybdenum silicide and/or MowSixNyOz, where w, x, y and z are numbers greater than zero), and/or opaque material (such as, for example, chromium). The projecting features 20 and the windows 22 together create the pattern in the radiation passing through reticle construction.
Only a fragment of the reticle construction 10 is shown in FIG. 1, and such fragment is part of a so-called main-field portion of the reticle. The main-field portion is a part of the reticle having windows therein for patterning radiation to ultimately form circuit elements associated with a semiconductor assembly. The reticle will typically also have a boundary portion extending around the main-field portion. The boundary portion has the primary function of blocking the light, but can have some patterned regions therein corresponding to non-circuit elements (i.e., patterned regions which do not form circuit elements associated with a semiconductor assembly). The patterned regions can be utilized for, among other things, calibration and mask alignment.
FIG. 2 shows a view from the bottom of the reticle construction 10, and diagrammatically illustrates the full construction to show that the reticle comprises a main-field region 30 containing the projecting features 20 and windows 22, and comprises a boundary region 32 surrounding the main-field region. The boundary region 32 will typically be covered by an opaque material (such as, for example, chromium) so that the boundary region blocks light from passing therethrough.
A continuing goal of semiconductor fabrication is to increase the density of structures formed across a semiconductor substrate (i.e., to increase the level of integration), which spawns a continuing goal to improve fabrication of the reticles utilized for patterning semiconductor substrates. Accordingly, it is desired to develop improved reticle constructions, and improved methods for forming reticle constructions.